Into the Mystic: ALMA ACA observations of the Mystic Mountains in Carina

TL;DR

This study uses ALMA ACA observations to analyze the structure, kinematics, and turbulence of the Mystic Mountains in Carina, revealing insights into the impact of UV radiation on molecular cloud dynamics and star formation.

Contribution

The paper provides high-resolution ALMA ACA data on the Mystic Mountains, comparing turbulence and structure under different radiation intensities, and introduces analysis of the turbulent driving parameter in this context.

Findings

Mystic Mountains form a coherent structure with continuous emission.

Turbulent driving parameter indicates similar turbulence modes to other pillars in Carina.

No clear correlation between gas velocity or turbulence and incident radiation was found.

Abstract

We present new observations of the Mystic Mountains cloud complex in the Carina Nebula using the ALMA Atacama Compact Array (ACA) to quantify the impact of strong UV radiation on the structure and kinematics of the gas. Our Band~6 observations target CO, $^{13}$CO, and C$^{18}$O; we also detect DCN J=3-2 and $^{13}$CS J=5-4. A dendrogram analysis reveals that the Mystic Mountains are a coherent structure, with continuous emission over $-$10.5 km s$^{-1}$ $<$ v < $-$2 km s$^{-1}$. We perform multiple analyses to isolate non-thermal motions in the Mystic Mountains including computing the turbulent driving parameter, $b$, which indicates whether compressive or solenoidal modes dominate. Each analysis yields values similar to other pillars in Carina that have been observed in a similar way but are subject to an order of magnitude less intense ionizing radiation. We find no clear correlation between the velocity or turbulent structure of the gas and the incident radiation, in contrast to other studies targeting different regions of Carina. This may reflect differences in the initial densities of regions that go on to collapse into pillars and those that still look like clouds or walls in the present day. Pre-existing over-densities that enable pillar formation may also explain why star formation in the pillars appears more evolved (from the presence of jets) than in other heavily-irradiated but non-pillar-like regions. High resolution observations of regions subject to an array of incident radiation are required to test this hypothesis.